Process of melt spinning roughsurfaced fibers



United States Patent 3,314,919 PROCESS OF MELT SPINNKNG RUUGH- SURFACEDFlIBER Elmer E. Most, Kinston, N.C., assignor to E. I. du Pont deNemours and Company, Wilmington, Del, a corporation of Delaware NoDrawing. Filed May 22, W62, fier. No. 196,615

2 Claims. (Cl. 260-4515) This invention relates to melt spun syntheticlinear condensation polymer textile fibers, and is more particularlyconcerned with modification of such fibers to provide improvedresistance to pilling and lower dynamic friction without adverselyaffecting other desirable properties.

Synthetic linear condensation polyester and polyamide textile fibers arewell-known in the art and, because of their outstanding properties, havefound application in many different end uses. These fibers are producedby melt-spinning the polymer into filaments and orienting the filamentsby drawing to several times the as-spun length. Textile yarns compriseeither these continuous fibers or staple fibers formed therefrom, as bycutting to lengths roughly corresponding to the better grades of cottonor wool. The natural fibers have rough surfaces, Whereas melt-spunfibers have had a smooth, shiny surface. This surface has madeprocessing into fabric more difiicult, because of the higher dynamicfriction, and has also been objectionable when an appearance similar tothat of natural fibers is desired.

The appearance of melt-spun fibers has been improved .by the use ofspinnerets which provide non round cross sections and by incorporatinginternal delustrants, such as finely-divided TiO in the polymer prior tospinning.

Graves US. Patent 2,205,722. and Dickson et al. British Patent 610,137disclose the use of a variety of internal delustrants which areinsoluble in the polymer and have a different refractive index. Thesefunction by scattering light which passes into the fiber but do notappreciably modify the fiber surface. They do not overcome the problemof high dynamic friction and create a new problem by increasing the rateof light aging.

A further problem with the melt spun condensation polymers, when used inthe form of staple fibers, is the tendency to form pills on textilefabrics. These are small but unsightly balls of snarled fiber endswhich. form when the surface of the fabric is rubbed during normalwearing. Extensive efforts have been made to overcome this problemwithout achieving fully satisfactory results.

An object of this invention is to produce melt spun fibers which areimproved in the above respects without adversely affecting otherdesirable properties. Gther objects will become apparent from thespecification and claims.

In accordance with this invention I have found that fibers, produced bymelt-spinning a synthetic linear condensation polymer and drawing thespun filaments into oriented fibers, are improved by incorporating inthe polymer 0.1 to 5% of a finely-divided (up to 100 micron)terephthalate salt of a metal of atomic number 20 to 56 from Group II ofthe Mendeleeff Periodic Table, e.g., calcium terephthalate, bariumterephthalate, cadmium terephthalate and zinc terephthalate. Manganeseterephthalate is also suitable. The preferred salt is calciumterephthalate. The preferred condensation polymers are polyethyleneterephthalate and polyhexamethylene adipamide, which may be modifiedwith minor amounts of copolymerizable components in accordance withcommercial practice.

Addition of the metal terephthalate has been found to decrease thedynamic friction of the fibers and to increase the resistance to pillingof the staple fibers, as illustrated in the examples. This isaccompanied by a surface roughening which can be observed by examinationwith a microscope. Since the salt is compatible with the polymer anddoes not differ appreciably in refractive index, the effect is unlikethat of the internal delustrants mentioned above. However, the surfaceroughening produced by the metal terephthalate makes it possible toreduce the amount of internal delustrant without impairing theappearance of fabric composed of the fibers. The resistance to lightaging has been found to be greatly improved.

The terephthalate salt may be added to the reactants before thepolymerization, during the polymerization, or to the polymer melt at theend of the polymerization prior to melt spinning. It may be added to, orcoated onto, the solid polymer flake before melting. In thepolymerization of polyethylene terephthalate it is preferred to add theterephthalate salt as a glycol slurry in the early stages of thepolymerization.

The average particle size required depends on the denier of the yarn andmay be between 0.1 and 100;]. and prefably between 3 and 30 The particlesize referred to is that measured before the terephthalate salt is addedto the polymer. The polymers may be spun into fibers with round ornon-round cross section, e.g., ribbon-like and trilobal.

The concentration of terephthalate salt required depends somewhat on theparticle size and on the end use of the yarn. In staple yarn, aconcentration of between 0.5 and 2.5% of the salt with particle sizebetween 1 and 25a is suitable if a cotton-like staple is desired. Instaple for worsted fabrics with cover, between 1.0 and 4.0% by weight ofthe salt with particle size between 1 and 50 1. is preferred. Ingeneral, the aesthetics increase with increasing concentration andparticle size of the terephthalate within these ranges.

Example 1 The terephthalates of Ca, Ba, Mn, Zn, and Cd are prepared asfollows: A quantity of dimethyl terephthalate is heated overnight on thesteam bath with a 10% excess of 10% sodium hydroxide containing methylalcohol. The excess caustic is neutralized to phenolphthalein withhydrochloric acid, and the metal terephthalate is precipitated in afinely-divided condition by addition of a concentrated, aqueous solutionof the appropriate metal salt. Yields of the dry salt are between and182 grams (4% by weight based on the weight of the polymer) of each ofthe metal terephthalates prepared above are tumbled with ten pounds ofsemi-dull (0.3% TiO polyethylene terephthalate flake. Each ten poundbatch of flake is melt spun and drawn to give a 70-denier, 34-filament,ribbon cross-section yarn. The ribbon crosssection is produced with aspinneret having orifices of the type shown in FIGURE IX of Pamm et al.US. Patent No. 2,816,349. Two control yarns are prepared with only 0.3%TiO present as the insoluble material for comparison purposes.Examination of the filaments produced, under a microscope, reveals thatthose containing the metal terephthalate salt have a rough surface andan uneven profile, whereas the yarn containing only TiO are relativelysmooth surfaced and have a uniform profile.

Friction measurements on the above yarns give coemcients of dynamicfriction below 0.5 for all the yarns containing metal terephthalatesalt, while the control yarns have coefficients above 0.65 in the sametest.

Each batch of yarn is cut into 2 /2 inch staple and processed separatelyinto a spun yarn on the cotton system. The processability of the yarnscontaining the metal terephthalate salts is markedly better than that ofthe control yarns, showing reduced running tensions, im proveddraftability, reduced roll wrapping, and the like.

Each of the spun yarns is woven into a 2 x 2 twill fabric. The fabricsamples containing the metal terephthalate salts are characterized by ahandle which is definitely dryer (less slick) than the control sample.This fabric is then subjected to the ASTM Test for Pilling Resistance ofTextile Fabrics, described in D137559T, Section E, Random Tumble PillingTester. There are 620 pills per 35 square inches with the controlcontaining TiO but no calcium terephthalate. When 4% calciumterephthalate is present there are 460 pills per 35 square inches, amarked improvement in resistance to pilling. Substantially the sameresult is obtained for each of the other metal terephthalates.

Example 2 Polyethylene terephthalate containing 0.5, 1.0, and 1.5%calcium terephthalate is melt-spun into trilo-bal cross section, 1.5denier per filament yarn (modification ratio 1.6). The coefiicient ofdynamic friction is measured and compared to a control yarn preparedfrom polyethylene terephthalate without calcium terephthalate. The datain Table I clearly indicate the reduction in friction obtained by theaddition of calcium terephthalate to the polymer.

TABLE I Coeflicient of Calcium terephthalate: dynamic friction None 0.690.5% 0.545 1.0% 0.445 1.5% 0.33

Substantially equivalent results are obtained with each of the othermetal terephthalates of Example 1 and when the procedure is repeatedusing in place of polyethylene terephthalate a copolyester of 10%ethylene isophthalate and 90% ethylene terephthalate.

The coefficient of dynamic friction used here is conveniently measuredby draping a single filament over a cylindrical polished mandrel (180contact) with one end of the filament attached to a strain gauge, andthe other end attached to a free-hanging weight of about 0.3 gram. Thesurface of the mandrel is flooded with No. 50 mineral oil and themandrel rotated at a surface speed of about 120 cm./sec. in a directionwhich exerts tension on the strain gauge. The coefficient of friction fis calculated from the equation where T is the output tension, T is theinput tension, and

a is the angle of wrap in radians.

ratings are made on a 1-5 scale where 1 is very bad, is

excellent, and 3 is borderline. The results are presented in Table IIalong with the results of similar tests on fabrics prepared frompolyethylene terephthalate fiber 5 containing no calcium terephthalate.

The Schiefer frosting test is a modification of the Schiefer abrasiontest, ASTM-D117561T, Section E. In the modified test the fabric sampleto be tested is dyed a deep navy blue, mounted on a round stationarysample holder, and abraded by a crosscut-surfaced steel head with aneccentric circular motion using a 2-pound head weight and a 3,000 cycleexposure. Frosting, in the abraded area of the sample, shows up as alighter blue color against the deep blue of the unabraded background.

It is known that the use of low viscosity polymer overcomes the pillingproblem while at the same time introducing a frosting problem. The datain the table show that, by the use of calcium terephthalate, both thepilling 3O problem and the frosting problem are overcome.

Example 4 A solution of hexamethylene diammonium adipate is polymerizedto polyhexamethylene adipamide in a conventional melt polymerization(see U.S. Patent No. 2,163,636). During the polymerization, at atemperature of 210 C. and a pressure of 250 pounds per square inch gage,calcium terephthalate in a aqueous slurry 4 is added. Two polymers wereprepared, one having 2% calcium terephthalate in the 15 particle-sizerange, and the other having 2% calcium terephthalate in the 6-95nparticle-size range. These polymers (26 and 33 relative viscosity,respectively) were extruded, cast, cut to flake, and the melt-spun yarndrawn (2.9-3.2 draw ratio) to 70 denier/34 filament round cross-sectionyarns. The finish free yarn-over-yarn hydrodynamic friction (f lightdurability (Weather-Ometer tenacity half-life, T and appearance of theseyarns was determined. For comparison two controls were run, one with 2%and another with 0.02% O.1-5,u. particle size TiO The results are shownin Table III.

TABLE III 1 Light r'ty Additive Hydro- SUbJOClZlVG Rating of ItemAdditive Particle dynamic fi gP g Appearance Size in [L Friction fh(g/d.) T1

in Hours 1 2% calcium terephthalate. 1-5 0. 42 600-700 Equivalent to0.3% TiO;

(semidull) delustered. 2 2% calcium terephthalate 6-95 0. 42 600-700 66-nylon with highlights. 3 2% T102 0.1-5 0.55 -100 Verl ly 520d coveringpower but c a y. 4 0.02% T102 0.1-5 0.70 150-200 Poor covering power.

Example 3 Example 5 2% Calcium terephthalate (based on the weight of thepolymer) is tumbled with polyethylene terephthalate flake having arelative viscosity of 20. The flake is then spun into a 3 denierfilament, 200 filament round cross-section yarn, the yarn cut into a 2/2 inch staple and the staple spun into yarn and made into a 2 x 2 twillfabric. The fabric is rated for pilling in the Random Tumble PillingTester ofASTM D-1375-59T, Section E, and for frost- A solution ofhexamethylene diammonium adipate is polymerized to polyhexamethyleneadipa'mide of fiberforming viscosity in a conventional meltpolymerization.

70 The polymer is extruded in the form of a ribbon, quenched with water,and cut to flake. The polymer flake is tumbled with 2% by weight offinely-divided calcium terephthalate in which the size of the particlesranges from 2 to 30 microns. The mixture of polymer flake and ing by theSchiefer Frosting Rating (at 3000 cycles). The calcium terephthalatepowder is then melt spun and drawn in a conventional fashion to give aIS-clenier, monofilament yarn having the normal commercial physicalproperties, i.e., a tenacity of 5.9 g.p.d. at 28% elongation.

A second yarn sample is prepared by introducing the calciumterephthalate as a water slurry into the partially polymerizedpolyhexamethylene adipamide and then further polymerizing the mixture toproduce a fiberforming polymer. The polymer is extruded as a ribbon,quenched, cut to flake, and then melt spun and drawn to give a 15-deniermonofilament as described above.

For comparison purposes, a control 15-denier monofilament yarn isprepared which contains 0.3% TiO but no calcium terephthalate.

These yarns are then knit into ladies seamless hosiery using theIS-denier monofilament in the knee, calf, ankle, and foot sections. Asimilarly prepared 40-denier, 13- filament yarn is used in the welt,heel and toe sections. During knitting it is foundthat the lower, moreuniform surface friction of the yarn containing calcium terephthalateaffords better control of yarn running tension which results in improvedcontrol of the leg length of the hosiery. The yarn containing calciumterephthalate is found to give a variation in leg length of i% inch forall hosiery knitted from one yarn package. In contrast, the control yarngives a leg length variation of :15 inch for hosiery knitted from asingle yarn package. Improved length control is obviously a greatadvantage to the manufacturer of ladies hosiery.

As an additional advantage it is found that the hosiery knitted fromyarn containing calcium terephthalate has a markedly drier and lessslick hand than the control.

The above experiment in which calcium terephthalate is added by tumblingthe powder with polymer flake is repeated with calcium terephthalateconcentrations of 0.25% and 0.1% by weight. The described improvement inlength control in knitted hosiery is achieved in both yarns.

Substantially equivalent results are obtained when the yarns areprepared from polycaproamide instead of polyhexamethylenediamineadipamide.

Similar results are obtained with hosiery yarns prepared frompolyundecanoamide.

Example 6 Finely-divided calcium terephthalate, having a particle sizein the 2-5 micron range, is added to hot caprolactam in suflicientquantity to give a slurry having a concentration of by weight. Fifteenpercent water is then add-ed to prevent crystallization of thecaprolactam upon cooling, and the slurry run through a colloid mill tocomplete the dispersion of the calcium terephthalate and render theslurry stable to settling. The caprolactam slurry is then polymerized inthe usual fashion to give a low molecular weight polymer, which isextruded as a ribbon and cut to flake.

Eight parts of the flake prepared above is blended with 92 parts of anylon 66/6 (875/125 parts by weight) random copolymer which is free ofTiO (The 66/6 copolymer is prepared by copolymerization of caprolactamand the adipic acid salt of hexamethylene diamine, using the generalprocess described by Spanagel in US. Patent No. 2,163,636.) The blendedflake is melt spun using apparatus of the type described by Waltz in US.Patent No. 2,571,975, and then drawn according to the teachings ofBabcock in US. Patent No. 2,289,232. The yarn produced is a 20-deniermonofilament having a tenacity of 6 g.p.d. at a break elongation of 28%.

Examination of the filaments under a microscope shows that the yarncontains a random dispersion of particles ranging in size from about 2microns to about 50 microns. Most of the particles at the surface of thefilament are found to be covered by a thin skin of polymer. The internalparticles are each associated with a void which is larger than theparticle. The surface of the filament is visibly rough.

The coefficient of friction is determined on a rotating chrome pinflooded with mineral oil to give an f value of 0.69. In the same test a66/6 copolymer yarn containing no calcium terephthalate and n0 TiO gavean value of 0.91, and a similar filament containing only 0.3% TiO gavean f value of 0.86.

Example 7 Nylon 66/6 (87.5/ 12.5) random copolymer flake offiber-forming molecular Weight is tumbled with a methanol dispersion of2% calcium terephthalate containing 0.4% polyvinyl-pyrrolidone as anadhesive. The methanol is removed by vaporization and the polymer meltspun as in US. Patent 2,571,975 and drawn as in US. Patent No. 2,289,232to give a 20-denier monofilament. Measurement of the coefficient offriction gives an f value of 0.57, in contrast to the high value of 0.86given by a control yarn containing 0.3% TiO in place of the calciumterephthalate.

Example 8 A copolymer of polyethylene terephthalate containing 3 /2 molpercent of sodium-3,5-di(carbomethoxy)-benzenesulfonate is preparedaccording to the method of Grifling U.S. Patent No. 3,018,272, extrudedas a ribbon and cut to flake. The flake is tumbled with 4% finelydividedcalcium terephthalate and used as the sheath component in melt spinninga sheath-core yarn according to the teachings of Breen in US. Patent No.2,931,091, using unmodified polyethylene terephthalate homopolymer asthe core component. The filaments obtained show a high level of surfaceroughness, a spontaneous spiral crimp, and equilibrium crimpreversibility which depends upon humidity. Measurement of thecoeflicient of friction on a smooth chrome pin at a yarn speed ofy.p.m., with no mineral oil present, gives a value of 0.14. In contrast,a control yarn containing no calcium terephthalate, prepared inessentially the same way, gives a coefiicient value of 0.70.

The yarn prepared is cut to staple, blended with wool in a 55/45 ratio,spun into yarn, and woven into a tropical Weight fabric. In pillingtests, the fabric made from yarn containing calcium terephthalate isfound to be equivalent to an all-Wool fabric, whereas fabric in whichthe polyethylene terephthalate fiber contains no calcium terephthalateis found to give objectionable pilling.

Polyamides to which this invention is applicable include:polycaproamide, polyhexamethylenediamine adipamide,polyhexamethylenediamine sebacamide, the polyamide from1,8-diamino-n-octane and oxalic acid, the polyamide frombis-p-aminocyclohexylmethane and azelaic acid, the polyamide from'bis-p-aminocyclohexylmethane and sebacic acid, the polyamide fromm-xylylenediamine and azelic acid, the polyamide from p xylylenediamineand azelaic acid, the polyamide from m-xylylenediamine and adipic acid,the polyamide from Z-methyl-hexamethylenediamine and oxalic acid, andthe polyamide from hexamethylenediamine and isophthalic acid. Polyestersuseful in this invention include: the polymethylene terephthalatesdisclosed in US. Patent No. 2,465,319, poly(hexahydro-p-xylylene)terephthalate, copolymers of ethylene glycol with terephthalic acid andisophthalic acid, copolyesters containing 2 mol percent 5- sodiumsulfoisophthalic acid, and the like.

Since many diflerent embodiments of the invention may be made Withoutdeparting from the spirit and scope thereof, it is to be understood thatthe invention is not limited by the specific illustrations except to theextent defined in the following claims.

I claim:

1. In the production of textile fibers of polyhexamethyleneadipamide bymelt-spinning the polymer and drawing the spun filaments into orientedfibers, which fibers are conventionally delustered by incorporating Ti0in the polymer, the improvement for decreasing the dynamic friction ofthe fibers produced and increasing the resistance to Reierences Cited bythe Examiner UNITED STATES PATENTS 2,238,949 4/1941 Sehlack 8-1 15.52,342,823 2/1944 Schlack 260-78 2,345,700 4/1944 Dreyfus 260-78 8Spanagel 260-78 Whinfield et al. 260-75 Auspos et al. 260-75 Hostettleret a1. 260-783 Cramer 260-75 Matray et a1. 8-1155 Notarbartolo et a1.260-783 LEON J. BERCOVITZ, Prim ry Examiner.

10 J. A. SEIDLECK, D. E. CZAIA, R. W. GRIFFIN,

Assistant Exan'ziners.

1. IN THE PRODUCTION OF TEXTILE FIBERS OF POLYHEXAMETHYLENEADIPAMIDE BYMELT-SPINNING THE POLYMER AND DRAWING THE SPUN FILAMENTS INTO ORIENTEDFIBERS, WHICH FIBERS ARE CONVENTIONALLY DELUSTERED BY INCORPORATING TIO2IN THE POLYMER, THE IMPROVEMENT FOR DECREASING THE DYNAMIC FRICTION OFTHE FIBERS PRODUCED AND INCREASING THE RESISTANCE TO LIGHT AGING WHICHCOMPRISES REPLACING AT LEAST PART OF THE TIO2 WITH 0.1 TO 5%, BASED ONTHE WEIGHT OF THE POLYMER, OF A FINELY-DIVIDED NORMAL TEREPHTHALATE SALTOF A METAL OF ATOMIC NUMBER 20 TO 56 FROM GROUP II OF THE PERIODICTABLE.